Stepless variable stroke drive having a non-rotating cam

ABSTRACT

A stepless variable stroke drive particularly suitable for a bicycle transmission has a crank driven input element comprising a carrier housing journaled for rotation on a spindle. Mounted within the carrier, journaled on individual axles, radially spaced to the spindle, are four planet gears which engage an output sun gear. Recessed into one side of each planet gear is a concentric channel whose outer circumference is constructed with ratchet teeth and whose inner circumference journals a crank ring having pawls for engaging the ratchet teeth. The ring also has a follower which engages a cylindrical cam channel fixed on and adjustable to various eccentricities relative to the spindle. As the carrier housing rotates, the crank ring follower engages the cam channel causing the crank rings to angularly oscillate at an amplitude proportional to the cam channel eccentricity. Sequential intermittent engagement of the crank ring pawls with the planet gear ratchet teeth during a portion of each carrier revolution drives the sun gear at a constant speed which is a multiple of the input speed dependent on the cam eccentricity. 
     In another embodiment, the crank ring is eliminated and the planet gears each have a follower for engaging the eccentric cam channel. The carrier housing has slots for the planet gear axles which allow the planet gear to sequentially move to engage and disengage the sun gear for a selected portion of each planet gear&#39;s oscillation to accomplish a speed increase, decrease or reversal. Alternate manual and automatic controls are provided for both embodiments to adjust the cam channel eccentricity.

BACKGROUND OF THE INVENTION

My invention relates in general to drives and more particularly tostepless, variable ratio drives employing a variable stroke mechanism.

An important advance in the use of variable stroke drives for automatictransmissions was the Waddington drive described in U.S. Pat. Nos.3,803,932 and 3,874,253, and in pending U.S. patent application No.737,632. The Waddington drive of these earlier descriptions employed acam which rotated at the input speed to the drive and which wasautomatically controlled to assume various eccentricities relative tothe center of input rotation in order to vary the stroke and thereby thetorque ratio of the drive. The instant invention also utilizes avariable stroke drive, but has the feature of a nonrotating cam whichallows manual control of the cam eccentricity to regulate the stroke andtorque ratio of the drive. The manual control capability is desirable insome situations as, for example, when the drive is used for a bicycletransmission. The manual control would accommodate cyclists who wouldprefer to manipulate the control themselves to suit their particularneeds. Indeed the drive is particularly attractive for use as a bicycletransmission because of its compactness, light weight, moderate cost andimmediate adaptability to existing bicycle frames. The earlierWaddington drives were either somewhat heavier because they operated atslow input speed and utilized large overrunning clutches, or requiredsome modification to the standard bicycle frame to incorporate an inputspeed stepup mechanism.

SUMMARY OF THE INVENTION

The invention is a variable stroke drive wherein the input elementcomprises a crank driven carrier housing journaled for rotation on aspindle. In the carrier, journaled on individual axles, are four planetgears which mesh with a sun gear. Recessed into one side of each planetgear is a concentric channel with ratchet teeth in its outercircumference. Journaled on the inner circumference of the channel is acrank ring having several pawls to engage the ratchet teeth. The crankring also has a follower which engages a cylindrical cam channel fixedon and adjustable to various eccentricities relative to the spindlecenter. Rotation of the carrier housing by the input means imparts tothe crank ring an angular oscillation of an amplitude proportional tothe eccentricity of the cam channel. As a crank ring is carried aroundthat quarter of a carrier revolution where it is oscillated at highestangular velocities in a direction opposite to the carrier rotation, thepawls of the ring engage the planet gear ratchet teeth and causerotation of the planet. The sequential engagement of the rings andplanets drives the sun gear at a substantially constant output speedwhich is a multiple of the input speed and is dependent on the cameccentricity.

Another embodiment of the invention eliminates the crank rings andratchet teeth. Instead, the planets are provided with a follower whichengages the cam channel and oscillates the planets. Provided in thecarrier housing are slots for the planet axles which allow the planetssequentially to move to engage and disengage the sun gear during aselected portion of the carrier revolution to accomplish a speedincrease, decrease or reversal.

The invention provides three alternate control mechanisms for adjustingthe eccentricity of the cam to shift the drive's ratios. The first is amanually manipulated arrangement of lever and cable. The second is anautomatic input speed control which utilizes centrifugal weights toengage an outer race when the input speed is above a predetermined valueand an inner race when below another value. The races, through a geararrangement, drive a screw which is linked to the cam. The third controlis automatic and responds to the torque across the drive.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view in section of an embodiment of the invention as itmay be applied for use as a bicycle transmission.

FIG. 2 is a section along the line 2--2 of FIG. 1.

FIG. 3 is a section along the line 3--3 of FIG. 1.

FIG. 4 is a side view, partly in section, of a manual control forshifting the transmission.

FIG. 5 is a section along the line 5--5 of FIG. 4.

FIG. 6 is an end view of the transmission with a torque ratio controlsensitive to input speed which is part of the invention.

FIG. 7 is a section along the line 7--7 of FIG. 6.

FIG. 8 is a section along the line 8--8 of FIG. 6.

FIG. 9 is a side view in section of another embodiment of the inventionas it may be applied for use as a bicycle transmission.

FIG. 10 is a section along the line 10--10 of FIG. 9.

FIG. 11 is a section along the line 11--11 of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1, 2 and 3, the transmission 10 is mounted by fixingits main spindle 12 in slotted left and right brackets 14 and 16 whichare attached to the bicycle rear fork members 18 and 20.

Screwed on the left side of the spindle 12 is a nut 22 which isprevented from turning by its two flats 24 which snugly fit a recess inthe left bracket 14. The bracket 14 is clamped between nut 22 and washer26 by end nut 28.

Similarly screwed on the right side of spindle 12 is pivot hub 30 whichis prevented from turning by its end flats 31 which fit into a recess inright bracket 16. The bracket 16 is clamped between the pivot hub 30 andwasher 32 by end nut 34. The nut 22 and pivot hub 30 are justsufficiently spaced on spindle 12 for intermediate parts to turn freely.

Adjacent pivot hub 30 is a carrier assembly 36 comprised of a sprocket38, a left side disk 40 and a cover 42. The sprocket 38 is journaled bya bearing 44 onto the spindle 12. An output sun gear 46 is journaledthrough its hollow shaft 48 onto spindle 12 by a pair of bearings 50.The carrier left side disk 40 is then journaled onto the shaft 48 by abearing 52.

The carrier 36 retains four axles 54 on each of which is a planet gear56 journaled by a bearing 58. The planets 56 have external teeth meshingwith sun gear 46. Recessed into one side of each planet 56, concentricwith the planet axle 54, is a channel 60. The outer circumference of thechannel 60 has a number of ratchet teeth 62. The inner circumferencesupports a bearing 64 for journaling a crank ring 66 received by channel60 on which are pivotally mounted several outward oriented pawls 68,shown in FIG. 3, to engage the ratchet teeth 62. Also in the crank ring66, for each pawl 68, there is a small bore 70 which retains acantilever spring 72 engaging a recess in its pawl 68 and urging thepawl 68 against the ratchet teeth 62. Retained in a recess in the outercircumference of the channel 60, protruding slightly beyond the ratchetteeth 62 is a resilient ring 74, seen in FIG. 1, on which the pawls 68noiselessly ride when not engaged.

Each crank ring 66 has a crank pin 76 protruding through an arcuate slot78 in the sprocket 38 as best seen in FIG. 3. Journaled on each crankpin 76 is a cylindrical follower 80 which follows a circular cam channel84 constructed in cam plate 88. Cam plate 88 is in turn journaled ontocam plate axle 82 by bearings 86.

As seen in FIG. 2, the cam plate axle 82 has a circular, interior bore90, the center P of which being offset from the geometric center C ofthe cam plate axle 82 and the center of the circular cam channel 84. Bymeans of the bore 90, the cam plate axle 82 is itself journaled ontocylindrical surface 92 of the pivot hub 30. The center P of cylindricalsurface 92 on the pivot hub 30 is offset from the spindle axis S by thesame distance that the center of the interior bore 90 in the cam plate88 is offset from the geometric center C of the cam plate axle 82. Thecam plate axle 82 is rotatably adjustable from concentricity to varyingeccentricities relative to the spindle 12 by pivoting about the center Pof surface 92. In order to reduce the loads on the follower 80, camplate 88 is freely rotatable on bearings 86.

Into the cam plate axle 82 is threaded a stop pin 94 which protrudesinto a groove 96 angularly spanning 90° of cylindrical surface 92 of thepivot hub 30 in order to limit the adjustability of the cam plate axle82. In FIG. 2 the center C of cam plate axle 82 is shown swung aroundthe pivot hub center P to its maximum eccentricity relative to spindlecenter S. A plastic dust cover 98 is provided to protect the cam plateaxle 82 and cam plate 88. The means employed for controlling theposition of cam plate 88 will be described subsequently. An output wheelhub 102 is journaled onto the output sun gear shaft 48 by a pair ofoverrunning clutches 100. The hub retains spokes 104 for mounting awheel (not shown) in the usual way. A washer 106 is interposed betweenthe hub 102 and the nut 22.

In operation the sprocket 38 of the bicycle transmission 10 is rotated(clockwise as viewed in FIG. 2) by a chain 108 driven by a foot crank(not shown) having pedals manipulated by the cyclist. The planet axles54, being mounted in the carrier 36, of which the sprocket 38 is a part,are rotated on the spindle 12. With the cam plate axle 82 positionedconcentric to the spindle 12, the angular position of each follower 80relative to its corresponding planet axle 54 is maintained throughout arevolution of the carrier 36. Therefore, the cranks 66 are motionlessrelative to the carrier 36. Because the planets 56 mesh with the outputsun gear 46, and the sun gear 46 resists rotation because it isconnected to the bicycle wheel, the planets 56 tend to rotate clockwiseabout their axles 54, but are prevented from such rotation by engagementof the pawls 68 with the ratchet teeth 62. The planets 56 are therebyconstrained relative to the carrier 36 and directly transmit the inputrotation of the carrier 36 to the sun gear 46. The rotational motion ofthe sun gear 46 is further transmitted by the overrunning clutches 100to the output hub 102 and the wheel spokes 104. With the cam channelconcentric with the spindle, no speed change occurs across thetransmission inasmuch as all of the rotating members are effectivelylocked together. Coasting with the chain pedals held motionless ispossible with a minimum of transmission frictional drag as theoverrunning clutches 100 allow the output hub 102 to turn easily on thesun gear shaft 48. Without this feature, coasting could be accommodatedby disengagement of the pawls allowing the planets to rotate within thecarrier.

When the cam channel 84 is eccentric to the spindle as the carrierrevolves, each follower oscillates its radial position toward and awayfrom the spindle. Since each axle is fixed in the carrier at a constantdistance from the spindle, this causes each follower to oscillate itscrank, i.e., to rotate the crank about its axle in one direction andsubsequently in the opposite direction. Since the four axles arecircumferentially equally spaced in the carrier, each crank isone-quarter of a cycle out of phase with its adjacent cranks.

So long as a crank rotates with a velocity opposite to, or at a velocityless than that of its planet, the crank pawls ride over the ratchetteeth in that planet. However, as the planet enters that quarter of acarrier revolution where the cam channel eccentricity imparts arotational velocity to the crank which is in the same direction as, andwhich begins to exceed that of its planet, its pawls engage. Forapplication of the drive as a bicycle transmission, virtually continuousengagement of the drive's input elements with the load is desirable, orthe cyclist will sense engagements as unpleasant jerkiness in thepedals. Consequently a high resolution pawl and ratchet arrangement isshown here.

Only 2° of rotation of the crank in a direction opposite to the planetrotation can take place before a pawl engages inasmuch as the spacing ofthe five pawls equally divides the 10° angular span of one ratchettooth. Thus for substantially a quarter of a carrier revolution, each ofthe four cranks is sequentially rotated relative to its planet so thatits pawls engage. The engaged crank then drivingly rotates its planetabout its axle in a direction opposite to the carrier rotation. Thisdriving planet imparts to the meshing sun gear a rotational velocityequal to the velocity of the planet about its axle plus the rotationalvelocity of the carrier. The remaining planets are rotated by the sungear at the same velocity as the driving planet, and thus their cranksare disengaged during this interval.

The planets sequentially drive the sun gear so that its resultant motionis substantially uniform corresponding approximately to the maximumrotational velocity of the planets superimposed on the velocity ofcarrier 36. The eccentricity of the cam channel 84 determines the outputvelocity and, hence, the speed and torque ratios of the drive.

The fixed nature of the cam channel 84 in this invention allows use of avariety of means for controlling its channel eccentricity. The cameccentricity can be adjusted at any time by the cyclist with the manualcontrol 110 shown in FIGS. 2, 4 and 5. The control 110 comprises a cable112 attached at one end to the cam plate axle 82 by a pin 114 so thatthe axle 82 can be pivoted of hub 30 toward greater eccentricity againstthe forces exerted by the followers 80 which tend to pull the cam plate88 toward zero eccentricity. A spring 116 is attached to ensurereturning of the axle 82 to zero eccentricity when the tension in thecable 112 is released. The cable 112 is routed through a protectivesheath 118 to a drum 120 in which the other end of the cable 112 isretained. The drum 120 is journaled on the hub of the adjacent lockingplate 122 which itself is journaled on a cylindrical extension of thecontrol support bracket 124 attached to the bicycle crossbar 126.Adjacent to the locking plate 112 and also journaled on the lockingplate hub is a front plate 128 which is retained thereon by a washer 130and a screw 132 threaded into the cylindrical extension of the bracket124. A second screw 133 passed through an extension of the front plate128 and threaded into an extension of the drum 120 pivotally supports alever 134 for locking the drum 120 in a desired angular position.

A spring 136 integral with the front plate 128 urges the lever 134 topivot so that its locking surface 138 bears against the locking plate122. The lever locking surface 138 is curved so that increased bearingpressure is produced as the tension in the cable 112 is increased. Thelever 134 is released allowing repositioning of the drum when thecyclist manually pivots the lever 134 in a counterclockwise direction asviewed in FIG. 4.

A control 140 sensitive to input speed for automatically adjusting theeccentricity of cam channel 84 to vary the transmission torque ratio maybe provided as shown in FIG. 6 and FIG. 7. The control housing issupported from the spindle 12 and the rear fork 20. A U-shaped bracket144 is spaced from and attached to the cam plate axle 82 by spacers 146and screws 148. The ends of a link 150 are respectively pivotallyconnected to the bracket 144 and to the end of a threaded shaft 152which is screwed into a hollow shaft 154 integral with a bevel pinion156. The pinion shaft 154 is journaled by ball bearings 158 having anouter race 160 retained by the housing 142.

A location adjusting nut 162 and a locking nut 164 are threaded onto thepinion shaft 154. Meshing with the pinion 156 on the left side of thepinion axis is a left bevel gear 166, and on the right side, a rightbevel gear 168. The right bevel gear 168 is fixed on a shaft 170extending from the inner clutch race 172. The inner clutch race 172 isencircled by the outer clutch race 174 which has a hub journaled on theshaft 170. The left bevel gear 166 is fixed on the hub of the outerclutch race 174.

A pin 176 fixed in the housing 142 journals the shaft 170 and thecontrol input sprocket 178. The input sprocket 178 supports acentrifugally responsive mechanism 180 between the inner and outerclutch races 172 and 174. The centrifugal mechanism 180 comprises twoarcuate weights 182 each having an inner groove 184 running the entireinner circumference and an outer groove 186 running the entire outercircumference thereof. The weights are retained on a ring 188 which fitsloosely and entirely within the inner circumference grooves 184 by agarter spring 190 which fits entirely within the outer circumferencegrooves 186. The ring 188 has two ears 192 mounted on pins 194projecting from the input sprocket 178 so that when the sprocket 178 ismotionless the inner circumferences of the weights 182 contact the innerrace 172. The input sprocket 178 may be driven by the same chain 108which drives the transmission 10.

In operation, when the control input sprocket 178 is rotated at lessthan a predetermined speed, the weights 184 contact and rotate the innerrace 172. The right bevel gear 168 rotates the pinion 154 so that thethreaded shaft 152 is screwed from the pinion shaft 156 and the camplate axle 82 is pushed to a position of lower eccentricity. When thecontrol input sprocket 178 is rotated at greater than a predeterminedspeed the weights 184 contact and rotate the outer race 174. The leftbevel gear 166 rotates the pinion 154 so that the threaded shaft 152 isscrewed into the pinion shaft 156 and the cam plate axle 82 is pulled toa position of greater eccentricity. The centrifugal mechanism 180 isdesigned so that the weights are not engaged over the optimum pedallingspeed range of a cyclist which is normally 50 to 60 revolutions perminute.

Thus if a cyclist pedalling within this optimum speed range encounters ahill and allows his pedalling speed to drop out of this range because ofthe increased torque required for pedalling, the speed control 140 willautomatically and continuously downshift the transmission toward a lowerinput-to-output speed ratio until the input pedalling torque required isreduced so that the cyclist is again able to pedal in the optimum speedrange. Opposite circumstances will produce upshifting.

Another embodiment of the invention illustrated in FIGS. 9-11 is thetransmission 200. It is identical to the transmission 10 previouslyillustrated with the exception of the cranks and planetary gears. Eachplanet 56' is journaled on an axle 54' retained by the carrier 36' aspreviously described. The carrier 36' is comprised of the sprocket 38'and the left disk 40' screwed and having slots 202 in which the axles54' can move to engage and disengage with the sun gear 46'. A crank pin76' integral with the planet 56' protrudes through an arcuate slot 78'in the sprocket 38' and journals a follower 80' which engages the camchannel 84' contained in cam plate 88'. Thus a revolution of the carrier36' causes a crank pin 76' to angularly oscillate its planet 56' aboutits axle 54' through one cycle.

By sequentially engaging each of the four planets with the sun gear onlyover a given portion of a carrier revolution, a speed increase, decreaseor reversal can be accomplished. For instance, by sequentially engagingeach of the planets with the sun gear over a portion of a carrierrevolution where a planet has highest angular velocities in a directioncommon to the carrier rotation, a speed decrease, or even a speedreversal can be accomplished. However, for a bicycle transmission, aspeed multiplication is desired. Thus by sequentially engaging each ofthe planets so that each planet drives the sun gear when that planet hashighest angular velocities in a direction opposite to the carrierrotation, a speed multiplication is accomplished. By using four planets,as shown in FIG. 3, and sequentially engaging each planet forsubstantially a quarter of a revolution when each planet has highestangular velocities opposite to the carrier, a multiplied andsubstantially constant output speed is obtained.

Retained in a groove cut into the gear teeth on the planets 56' is aring 74' of resilient material upon which the planets 56' noiselesslyride when not engaged with the sun gear 46'. Several means are providedto engage a planet over the desired driving quadrant, whereasdisengagement tends to occur spontaneously as a planet leaves thedriving quadrant because the planet and sun gear velocities are forcedto become disparate.

One engagement means is to mount the transmission 200 with therotational plane of the carrier 36' oriented vertically and with thegeometric center of the cam plate axle 82' displaceable to maximumeccentricity to the left of the spindle 12'. With the carrier 36'rotating clockwise as seen in FIG. 10, and the crank pins 76' arrangedto trail their respective planet axles 54', a planet 56' thereforerotates counterclockwise at maximum velocity when at the top of thecarrier 36'. This is the center of the quadrant over which it is desiredto have a planet drive the sun gear for the bicycle application. Theslots for the planet axles are oriented so that as a planet enters thedesired driving quadrant, gravity can bring the planet toward the sungear. Moreover, with the crank pins arranged to follow the planet axles,the reactant cam force on the follower pushes the planet toward the sungear as a planet enters the desired driving quadrant. Also, thefrictional drag on the rim of the planet produced by the sun gear actsto pivot the planet about its crank pin into engagement with the sungear. Additionally, springs 204 may be provided to urge the planets 56'against the sun gear 46'.

Any of the means already described for adjusting the cam channeleccentricity may be used to vary the speed and torque ratios of thisembodiment. Yet another means, which automatically adjusts the camchannel eccentricity as a function of the torque applied across thetransmission, equally applicable to both embodiments, is shown in FIG.11. A U-bracket 144' is mounted to the cam plate axle 82 and pivotallyattached to a link 150' which in turn is pivotally attached to theplunger 206 of a dashpot 208. The dashpot 208 is fixedly mounted on anyconvenient rigid member of the bicycle frame.

The plunger 206 is loaded by a spring 210 so that as the cam plate axle82' is moved from maximum to low eccentricity, an increasingly resistantforce is applied. When a follower is turning a planet at highestvelocities counter to the carrier velocity, the follower applies thehighest forces experienced by the cam channel 84, in a direction fromthe center of the cam channel to the center of the follower. The centerof the large cylindrical surface of the pivot hub 30, which is theeffective pivot point for the cam plate axle 82, is offset from the lineof action of the follower force so that the cam plate axle 82 is urgedto pivot toward zero eccentricity. In operation, as the bicycle beginsto climb a hill for instance, the output torque requirement increasesand a greater force is applied by the followers against the cam channel.If the cyclist continues to pedal at the same rate, this increased forceis balanced by the shifting of the cam plate axle 82 against the springto lesser eccentricity. The decreased speed multiplication and increasedtorque multiplication of the transmission allow the cyclist to pedal atthe same input torque as previously used, but, of course, with reducedoutput speed. Proper selection of the spring 210 will allow a cyclist topedal at his optimum speed and torque while the transmissionautomatically adjusts to meet varying output torque requirements. Thedashpot 208 is provided to prevent the transmission 200 from cyclicallyresponding to the variable torque applied by the cyclist to the footpedals during a revolution of the foot crank.

Although four planet gears have been shown in the drawings and mentionedin the description, the number used depends on the particularrequirements of the application. In the case, for instance, where asingle cylinder engine is employed to drive the transmission, a singleplanet, engaging the output gear during the power stroke of the enginemay be used in conjunction with a flywheel for providing motion for theparasitic strokes.

Having thus described the invention, what is claimed as novel anddesired to be secured by Letters Patent of the United States is:
 1. Astepless variable stroke drive comprising:a carrier housing journaled ona spindle for rotation about the axis of the spindle, said carrier beingoperatively connected to means for rotatably driving said carrier; atleast one crank ring mounted in the carrier for rotation about an axisradially offset from the axis of the spindle, said crank ring having afollower rotatably mounted on a pin extending outward therefrom; a camplate mounted on the spindle for selective pivotal movement throughvarious positions of eccentricity relative to the axis of the spindle;cam channel constructed on said cam plate in a position to receive thecrank follower and to cause the crank ring to angularly oscillate withan amplitude which varies directly proportional to the cam channeleccentricity when the carrier is rotated; means connected to the camplate to selectively vary the eccentric position thereof; first meansoperatively connected to the crank ring for selectively transmitting theangular motion thereof; second means operatively connected to thecarrier and the crank ring transmitting means to receive motion thereofand to transmit the summation of the motions of said carrier and saidcrank ring; and an output mechanism operatively connected to the secondtransmitting means.
 2. A stepless variable stroke drive as described inclaim 1 wherein a plurality of crank rings are mounted on the carrierradially offset from the axis of the spindle and angularly spacedthereon; said crank rings being operatively associated with an equalplurality of first and second transmitting means.
 3. A stepless variablestroke drive as described in claim 1 wherein the second transmittingmeans comprises:a planet gear mounted on the carrier for rotation aboutan axis radially offset from the axis of the spindle, said gear havingteeth constructed on its outer periphery for engagement with the outputmechanism, said planet gear also being constructed with an annularchannel adapted to receive the crank ring for rotation about the axis ofsaid planet gear and operatively connected to the first transmittingmeans for receiving the motion transmitted thereby.
 4. A steplessvariable stroke drive as described in claim 3 wherein the firsttransmitting means comprises:ratchet teeth constructed in the outer wallof the planet gear channel; and a plurality of pawls mounted on thecrank ring for engagement with the ratchet teeth during selectedportions of the angular motion of the crank ring.
 5. A stepless variablestroke drive as described in claim 3 wherein the output mechanismcomprises:a sun gear mounted for rotation on the spindle and positionedto operatively engage the planet gear.
 6. A stepless variable strokedrive as described in claim 5 wherein the output mechanism furthercomprises a hub mounted on the spindle and operatively connected to thesun gear through a clutch.
 7. A stepless variable stroke drive asdescribed in claim 1 wherein the cam plate is mounted on the spindle bymeans comprising:a cylindrical hub mounted on the spindle axis, thecenter axis of said hub being offset from the spindle axis; and journalmeans mounted on the cylindrical surface of the hub and adapted toreceive the cam plate for pivotal motion about the center axis of thehub, the center axis of said cam plate being offset from the center axisof the hub and from the spindle axis such that, by pivoting the camplate on the hub, the distance that the center axis of the cam plate isoffset from the spindle axis is varied.
 8. A stepless variable strokedrive as described in claim 7 wherein the journal means comprises acylindrical cam plate axle mounted on the cylindrical surface of the hubfor pivotal motion about the center axis of the hub, the center axis ofsaid plate axle being offset from the center axis of the hub and fromthe center axis of the spindle such that, by pivoting the plate axle onthe hub, the distance that the center axis of the cam plate axle isoffset from the spindle is varied, said plate axle being adapted toreceive the cam plate for free concentric rotation thereon.
 9. Astepless variable stroke drive as described in claim 7 wherein thedistance that the center axis of the hub is offset from the spindle axisis equal to the distance that the center axis of the cam plate is offsetfrom the center axis of the hub, thereby allowing the center axis of thecam plate to be moved in an arc from a concentric position with respectto the spindle axis to eccentric positions with respect to the spindleaxis.
 10. A stepless variable stroke drive as described in claim 7wherein the means for varying the eccentric positon of the cam platecomprises:a first cable attached to the cam plate at one end and beingspring biased at its other end to exert a pivotal force on the cam platetending to maintain the cam plate in the concentric position; and asecond cable fixed to said cam plate at one end and to an actuatinglever at its other end, actuation of said lever exerting a pivotal forceon the cam plate tending to pivot the cam plate about the center axis ofthe hub and vary the eccentric position of the cam plate with respect tothe spindle axis.
 11. A stepless variable stroke drive as described inclaim 10 wherein the actuating lever comprises:a support bracket havinga cylindrical hub extending therefrom; a support plate mounted forpivotal movement on the hub of the support bracket and having an armextending radially outward therefrom; an actuating arm pivotallyattached to the extension arm of the support plate to extend radiallyinward and outward therefrom; said arm being constructed with a roundedlocking surface at its radially innermost end; a locking plate journaledon the hub of the support bracket adjacent to the support plate, saidlocking plate having a generally rounded surface extending radiallyoutward to engage the locking surface of the actuating arm; resilientmeans operatively engaging the actuating arm to urge said arm in lockingengagement with the locking plate; and a drum mounted on the hub of thesupport bracket for rotation with the support plate; said drum adaptedto receive the cable about its circumference to cause retraction orextension of the cable as the drum is rotated.
 12. A stepless variablestroke drive as described in claim 7 wherein the means for varying theeccentricity of the cam track comprises:a support housing mounted on thespindle; a pinion gear mounted for rotation within the housing andhaving a cylindrical portion extending axially therefrom, saidcylindrical portion having an axially oriented concentric receptacleconstructed with interior threads; a threaded shaft engaged in thereceptacle of the pinion gear and extending axially outward therefrom,said shaft being connected to the cam plate so that axial movement ofthe shaft causes pivotal movement of the cam plate on the hub; an axlemounted for rotation in the housing about an axis transverse to the axisof the pinion gear, said axle adapted to receive an input member forrotation thereon; first and second bevel gears mounted for rotation onthe axle and positioned to engage opposite sides of the pinion gear, sothat, when the first bevel gear drives the pinion gear, the threadedshaft extends and, when the second bevel gear drives the pinion gear,the threaded shaft retracts; inner and outer clutch races separatelymounted for rotation on the axle and each constructed with axiallyextending radially spaced opposing flanges, said inner race connected tothe first bevel gear for rotation therewith and said outer raceconnected to the second bevel gear for rotation therewith, and acentrifugal ring element constructed to radially expand or contactproportionally to speed, mounted on the input member for rotationtherewith, said ring extending into the space between the flanges of theinner and outer clutch races and radially positioned therein to engagethe inner race at relatively low rotational speeds and to engage theouter race at relatively high rotational speeds.
 13. A stepless variablestroke drive as described in claim 7 wherein the means for varying theeccentric position of the cam plate comprises:a yoke fixed to the camplate at a position radially spaced from the pivot axis thereof andhaving an arm extending tangentially outward from the cam plate; aconnecting link pivotally connected to the outer end of the yoke arm;and a spring biased piston and cylinder means, the piston shaft of whichbeing pivotally connected to the connecting link, said spring exerting aforce on the piston which tends to pivot the cam plate to greatereccentricity and being selected to balance the normal torque tending topivot the cam plate toward concentricity caused by the interactionbetween the follower and the cam plate and to expand or retract inresponse to changes in said torque.
 14. A stepless variable stroke driveas described in claim 1 wherein the means to rotatably drive the carrierhousing comprises:a toothed sprocket fixed to the carrier housing forrotation therewith; a rotating pedal driven crank; and a chainoperatively connecting the crank to the sprocket.
 15. A steplessvariable stroke drive as described in claim 1 wherein the secondtransmitting means comprises a set of gear teeth fixed to the outercircumference of the crank ring for engagement with the outputmechanism.
 16. A stepless variable stroke drive as described in claim 15wherein the first transmitting means comprises mounting meansconstructed in the carrier to support the crank ring for limited radialsliding movement, said movement allowing the crank ring to engage anddisengage the output mechanism during selected portions of the angularmotion of the crank ring.
 17. A stepless variable stroke drive asdescribed in claim 16 wherein the mounting means comprises an axleconstructed to support the crank ring for rotary motion about the axisthereof, said axle being mounted in a slot on the carrier for limitedradial sliding movement thereon, said slot being constructed to allowthe crank ring to engage and disengage the output mechanism duringselected portions of the angular motion of the crank ring as the carrierrotates.
 18. A stepless variable stroke drive as described in claim 17further comprising resilient means engaging the axle to urge the crankring into engagement with the output mechanism.
 19. A stepless variablestroke drive as described in claim 16 wherein the output mechanismcomprises:a sun gear mounted for rotation on the spindle and positionedto operatively engage the teeth of the crank ring.
 20. A steplessvariable stroke drive as described in claim 19 wherein the ouputmechanism further comprises a hub mounted on the spindle and operativelyconnected to the sun gear through a clutch.
 21. A stepless variablestroke drive for a bicycle, said bicycle having a frame which includesfront and rear forks adapted to receive wheel axes comprising:a spindlemounted on the rear axle fork; a carrier housing journaled on thespindle for rotation about the axis of the spindle; a toothed sprocketfixed to the carrier housing for rotation therewith; at least one crankring mounted in the carrier for rotation about an axis radially offsetfrom the axis of the spindle, said crank having a follower rotatablymounted on a pin extending outward therefrom; a cam plate mounted on thespindle for selective pivotal movement through various positions ofeccentricity relative to the axis of the spindle, a cam channelconstructed on said cam plate in a position to receive the crankfollower and to cause the crank ring to angularly oscillate with anamplitude which varies directly proportional with the cam channeleccentricity when the carrier is rotated; means connected to the camplate to selectively vary the eccentric position thereof; first meansoperatively connected to the crank ring for selectively transmitting theangular motion thereof; second means operatively connected to thecarrier and the crank ring transmitting means to receive the motionsthereof and to transmit the summation of the motions of said carrier andsaid crank ring; an output mechanism operatively connected to the secondtransmitting means; a hub mounted for rotation on the spindle andoperatively connected to the output mechanism, said hub adapted toreceive and support a bicycle wheel for rotation therewith; a pedaldriven crank rotatably mounted on the bicycle frame, forward of the rearfork, for actuation by the operator; and a chain operatively connectingthe crank to the sprocket.
 22. A stepless variable stroke drive asdescribed in claim 21 wherein a plurality of crank rings are mounted onthe carrier radially offset from the axis of the spindle and angularlyspaced thereon; said crank rings being operatively associated with anequal plurality of first and second transmitting means.
 23. A steplessvariable stroke drive as described in claim 21 wherein the secondtransmitting means comprises:a planet gear mounted on the carrier forrotation about an axis radially offset from the axis of the spindle,said gear having teeth constructed on its outer periphery for engagementwith the output mechanism, said planet gear also being constructed withan annular channel adapted to receive the crank ring for rotation aboutthe axis of said planet gear and operatively connected to the firsttransmitting means for receiving the motion transmitted thereby.
 24. Astepless variable stroke drive as described in claim 23 wherein thefirst transmitting means comprises:ratchet teeth constructed in theouter wall of the planet gear channel; and a plurality of pawls mountedon the crank ring for engagement with the ratchet teeth during selectedportions of the angular motion of the crank ring.
 25. A steplessvariable stroke drive as described in claim 23 wherein the outputmechanism comprises:a sun gear mounted for rotation on the spindle andpositioned to operatively engage the planet gear.
 26. A steplessvariable stroke drive as described in claim 25 wherein the hub isoperatively connected to the sun gear by a clutch.
 27. A steplessvariable stroke drive as described in claim 21 wherein the secondtransmitting means comprises a set of gear teeth fixed to the outercircumference of the crank ring for engagement with the outputmechanism.
 28. A stepless variable stroke drive as described in claim 27wherein the first transmitting means comprises mounting meansconstructed in the carrier to support the crank ring for limited radialsliding movement, said movement allowing the crank ring to engage anddisengage the output mechanism during selected portions of the angularmotion of the crank ring.
 29. A stepless variable stroke drive asdescribed in claim 28 wherein the mounting means comprises an axleconstructed to support the crank ring for rotary motion about the axisthereof, said axle being mounted in a slot on the carrier for limitedradial sliding movement thereon, said slot being constructed to allowthe crank ring to engage and disengage the output mechanism duringselected portions of the angular motion of the crank ring as the carrierrotates.
 30. A stepless variable stroke drive as described in claim 29further comprising resilient means engaging the axle to urge the crankring into engagement with the output mechanism.
 31. A stepless variablestroke drive as described in claim 28 wherein the output mechanismcomprises: a sun gear mounted for rotation on the spindle and positionedto operatively engage the teeth of the crank ring.
 32. A steplessvariable stroke drive as described in claim 31 wherein the hub isoperatively connected to the sun gear by a clutch.
 33. A steplessvariable stroke drive as described in claim 21 wherein the cam plate ismounted on the spindle by means comprising:a cylindrical hub mounted onthe spindle axis, the center axis of said hub being offset from thespindle axis; and journal means mounted on the cylindrical surface ofthe hub and adapted to receive the cam plate for pivotal motion aboutthe center axis of the hub, the center axis of said cam plate beingoffset from the center axis of the hub and from the spindle axis suchthat, by pivoting the cam plate on the hub, the distance that the centeraxis of the cam plate is offset from the spindle axis is varied.
 34. Astepless variable stroke drive as described in claim 33 wherein thejournal means comprises a cylindrical cam plate axle mounted on thecylindrical surface of the hub for pivotal motion about the center axisof the hub, the center axis of said plate axle being offset from thecenter axis of the hub and from the center axis of the spindle suchthat, by pivoting the plate axle on the hub, the distance that thecenter axis of the cam plate axle is offsef from the spindle is varied,said plate axle being adapted to receive the cam track for freeconcentric rotation thereon.
 35. A stepless variable stroke drive asdescribed in claim 33 wherein the distance that the center axis of thehub is offset from the spindle axis is equal to the distance that thecenter axis of the cam plate is offset from the center axis of the hub,thereby allowing the center axis of the cam plate to be moved in an arcfrom a concentric position with respect to the spindle axis and toeccentric positions with respect to the spindle axis.
 36. A steplessvariable stroke drive as described in claim 33 wherein the means forvarying the eccentric position of the cam plate comprises:a first cableattached to the cam plate at one end and being spring biased at itsother end to exert a pivotal force on the cam plate tending to maintainthe cam plate in the concentric position; and a second cable fixed tosaid cam plate at one end and to an actuating lever at its other end,actuation of said lever exerting a pivotal force on the cam platetending to pivot the cam plate about the center axis of the hub and varythe eccentric position of the cam plate with respect to the spindleaxis.
 37. A stepless variable stroke drive comprising:a carrier housinghaving a substantially circular cross section journaled on a spindle forrotation about the axis of the spindle, said carrier being operativelyconnected to means for rotatably driving said carrier; a set of fourcrank rings mounted in the carrier for rotation about an axis radiallyoffset from the axis of the spindle, each of said crank rings having afollower extending outward therefrom and said rings being spaced atsubstantially ninety degree intervals about the cross section of thecarrier; a cam plate mounted on the spindle for selective pivotalmovement through various positions of eccentricity relative to the axisof the spindle; cam channel constructed on said cam plate in a positionto receive each of the crank ring followers to cause the crank ring toangularly oscillate with an amplitude which varies directly proportionalto the cam plate eccentricity when the carrier is rotated; meansconnected to the cam plate to selectively vary the eccentric positionthereof; first means operatively connected to the crank rings forselectively transmitting the angular motion thereof; second meansoperatively connected to the carrier and the crank ring transmittingmeans to receive the motions thereof and to transmit the summation ofthe motions of said carrier and said crank rings; and an outputmechanism operatively connected to the second transmitting means.
 38. Astepless variable stroke drive as described in claim 37 wherein thesecond transmitting means comprises:a set of four planet gears mountedon the carrier at substantially ninety degree intervals for rotationabout an axis radially offset from the axis of the spindle, said gearshaving teeth constructed on their outer periphery for engagement withthe output mechanism, said planet gears also being constructed with anannular channel adapted to receive the crank rings for rotation aboutthe axis of said planet gears and operatively connected to the firsttransmitting means for receiving the motion transmitted thereby.
 39. Astepless variable stroke drive as described in claim 38 wherein thefirst transmitting means comprises:ratchet teeth constructed in theouter wall of each planet gear channel; and a plurality of pawls mountedon each crank ring for engagement with the ratchet teeth during selectedportions of the angular motion of the crank rings.
 40. A steplessvariable stroke drive as described in claim 38 wherein the outputmechanism comprises:a sun gear mounted for rotation on the spindle andpositioned to operatively engage the planet gears.
 41. A steplessvariable stroke drive as described in claim 40 wherein the outputmechanism further comprises a hub mounted on the spindle and operativelyconnected to the sun gear through a clutch.
 42. A stepless variablestroke drive as described in claim 37 wherein the cam plate is mountedon the spindle by means comprising:a cylindrical hub mounted on thespindle axis, the center axis of said hub being offset from the spindleaxis; and journal means mounted on the cylindrical surface of the huband adapted to receive the cam plate for pivotal motion about the centeraxis of the hub, the center axis of said cam plate being offset from thecenter axis of the hub and from the spindle axis such that, by pivotingthe cam plate on the hub, the distance that the center axis of the camplate is offset from the spindle axis is varied.
 43. A stepless variablestroke drive as described in claim 42 wherein the journal meanscomprises a cylindrical cam plate axle mounted on the cylindricalsurface of the hub for pivotal motion about the center axis of the hub,the center axis of said plate axle being offset from the center axis ofthe hub and from the center axis of the spindle such that, by pivotingthe plate axle on the hub, the distance that the center axis of the camplate is offset from the spindle is varied, said plate axle beingadapted to receive the cam plate for free concentric rotation thereon.44. A stepless variable stroke drive as described in claim 42 whereinthe distance that the center axis of the hub is offset from the spindleaxis is equal to the distance that the center axis of the cam plate isoffset from the center axis of the hub, thereby allowing the center axisof the cam plate to be moved in an arc from a concentric position withrespect to the spindle axis and to eccentric positions with respect tothe spindle axis.
 45. A stepless variable stroke drive as described inclaim 42 wherein the means for varying the eccentric position of the camplate comprises:a first cable attached to the cam plate at one end andbeing spring biased at its other end to exert a pivotal force on the camplate tending to maintain the cam plate in the concentric position; anda second cable fixed to said cam plate at one end and to an actuatinglever at its other end, actuation of said lever exerting a pivotal forceon the cam plate tending to pivot the cam plate about the center axis ofthe hub and vary the eccentric position of the cam plate with respect tothe spindle axis.
 46. A stepless variable stroke drive as described inclaim 37 wherein the means to rotatably drive the carrier housingcomprises:a toothed sprocket fixed to the carrier housing for rotationtherewith; a rotating pedal driven crank; and a chain operativelyconnecting the crank to the sprocket.
 47. A stepless variable strokedrive as described in claim 37 wherein the second transmitting meanscomprises a set of gear teeth fixed to the outer circumference of eachcrank ring for engagement with the output mechanism.
 48. A steplessvariable stroke drive as described in claim 47 wherein the firsttransmitting means comprises mounting means constructed in the carrierto support each crank ring for limited radial sliding movement, saidmovement allowing the crank rings to engage and disengage the outputmechanism during selected portions of the angular motion of each crankring.
 49. A stepless variable stroke drive as described in claim 48wherein the mounting means comprises an axle constructed to support eachcrank ring for rotary motion about the axis thereof, said axles beingmounted in a slot on the carrier for limited radial sliding movementthereon, said slot being constructed to allow the crank rings to engageand disengage the output mechanism during selected portions of theangular motion of each crank ring as the carrier rotates.
 50. A steplessvariable stroke drive as described in claim 47 further comprisingresilient means engaging the axles to urge the crank rings intoengagement with the output mechanism.
 51. A stepless variable strokedrive as described in claim 48 wherein the output mechanism comprises: asun gear mounted for rotation on the spindle and positioned tooperatively engage the teeth of the crank ring.
 52. A stepless variablestroke drive as described in claim 51 wherein the output mechanismfurther comprises a hub mounted on the spindle and operatively connectedto the sun gear through a clutch.